Bob Schoelkopf of the Marine Mammal Stranding Center in Brigantine says bulls sharks have been known to swim in the section of Navesink River near the Route 35 bridge.
He and others have been concerned about a worsening pattern of harassment by boaters and people on personal watercraft getting too close to the dolphins in Navesink.
Although no one has documented the presence of a bull shark in the river in recent weeks, Schoelkopf says a recent encounter sounds like it could have involved one.